ULTRASONOGRAPHIC STUDY OF THE STERNOCLEIDOMASTOID MUSCLE IN THE MANAGEMENT OF CONGENITAL MUSCULAR TORTICOLLIS

Background: Congenital muscular torticollis (CMT) in infancy is caused by the fibrotic change of the sternocleidomastoid muscle (SCMM). The etiology and management strategies remain controversial. Methods: One hundred ninety-seven infants and children aged 1 month to 16 years who had CMT were examined by real-time ultrasonography of the SCMM betwee n June 1995 and September 1996 in a prospective and longitudinal study . A total of 362 examinations were performed. There were 122 boys and 75 girls. Results: The right side was involved in 117 patients (59.3%) , the left side in 79 patients (40.7%), and both sides in one patient. The sonographic findings were homogeneous or heterogeneous (patchy) h yperechoic lesion within the SCMM, and all were diagnostic. The ultras onographic appearance of the SCMM in this study has a close resemblanc e to the clinical course of CMT. The extent of fibrosis as represented by the cross section of lesion to muscle ratio (L/M ratio) decreased from 83.6% at 2 months to 59.9% at 9 months of age and further decreas ed to 40% beyond 1 year of age. This consistent decrease in fibrosis w as caused by the increased normal muscle volume at the periphery and b y the regenerated muscle fibers within the lesion. In this series of 1 97 patients, 32 (16.2%) eventually underwent surgery to release the SC MM because of persistent bead tilt, chin deviation and limited range o f neck motion beyond 1 year of age. The L/M ratio of the operative gro up was 62.7 +/- 16.0% compared with an UM ratio of 54.5 +/- 14.2% (P = .035) for the nonoperative group at 1 year of age. The extent of fibr otic change in;he cross section of the muscle was a significant factor in determining prognosis. In the longitudinal section, the fibrotic c hange was limited to only the lower third of the SCMM in 27 patients, and all of them recovered without operation. in 95 patients, the fibro tic lesion was limited to the middle and lower third or middle third o nly, and only six (6.3%) underwent operation. However, in 75 cases the entire length of muscle was involved, and 26 (34.7%) required surgica l release of the contracted muscle. Whole-length muscle involvement wa s also important for predicting recovery without operative interventio n. Conclusions: Ultrasonographic study of the SCMM is not only a valua ble diagnostic tool but can also serve as a useful guideline for the t reatment of infants who have congenital muscular torticollis. Copyrigh t (C) 1997 by W.B. Saunders Company.